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Module 1.5b

your heart rate, which increases your alertness [Moorcroft, 2003].) When you are ready Waking beta waves
for bed, a researcher comes in and tapes electrodes to your scalp (to detect your brain
waves), on your chin (to detect muscle tension), and just outside the corners of your CONNECT 1.5-5
eyes (to detect eye movements) (Figure 1.5-4). Other devices may record your heart rate, Waking alpha waves
respiration rate, and genital arousal. Tell students that the electroenceph-
alogram (EEG), which is discussed
Left eye movements in Module 1.4a, is the device used
Stage 1 to measure sleep waves. This device
Right eye movements
captures the electrical activity given
off by the neurons as they fire action
EMG (muscle tension)
Stage 2
potentials. The speed with which the
action potentials (see Module 1.3a)
EEG (brain waves)
Hank Morgan/Science Source Stage 3 (delta waves) occur creates the brain wave patterns
seen during wakefulness and sleep.
TEACH 1.5-5

Figure 1.5-4 Rebecca Spencer, University of Massachusetts, assisted with this illustration. Enrichment
Direct students’ attention to
Measuring sleep activity REM
Sleep researchers measure brain-wave activity, eye movements, and muscle tension with Figure 1.5-5, which depicts beta
electrodes that pick up weak electrical signals from the brain, eyes, and facial muscles waves, the brain waves people exhibit
(Dement, 1978).
6 sec
when they are awake and active.
Figure 1.5-5 These are high-frequency low-
When you are in bed with your eyes closed, the researcher in the next room sees on the
EEG the relatively slow alpha waves of your awake but relaxed state (Figure 1.5-5). As time Brain waves and sleep amplitude waves. Theta waves
stages
wears on, you adapt to all this equipment, grow tired and, in an unremembered moment, The beta waves of an alert, characterize the transition from
slip into sleep (Figure 1.5-6). This transition is marked by the slowed breathing and the waking state and the regular
irregular brain waves of Stage 1 sleep. (Sleep stages 1, 2, and 3 are now called N1, N2, and alpha waves of an awake, relaxed Stage 1 to Stage 2. Theta waves are
N3 — indicating that they occur during NREM sleep.) state differ from the slower, larger slower in frequency and higher in
delta waves of deep Stage 3
sleep. Although the rapid REM amplitude than alpha waves, and are
sleep waves resemble the near-
waking Stage 1 sleep waves, the present as we move from relaxation to
body is more internally aroused deeper sleep.
Sleep 1 second during REM sleep than during
NREM sleep (Stages 1, 2, and 3).
Figure 1.5-6 Copyright © Bedford, Freeman & Worth Publishers.
The moment of sleep Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
Although we are unaware of the moment we fall into sleep, someone
watching our brain waves could tell (Dement, 1999).
In one of his 15,000 research participants, William Dement (1999) observed the moment alpha waves the relatively slow
the brain’s perceptual window to the outside world slammed shut. Dement asked this brain waves of a relaxed, awake
state.
sleep-deprived young man with eyelids taped open to press a button every time a strobe light
flashed in his eyes (about every 6 seconds). After a few minutes, the young man missed one. NREM sleep non-rapid eye
movement sleep; encompasses
Asked why, he said, “Because there was no flash.” But there was a flash. He had missed it all sleep stages except for REM
because (as his brain activity revealed) he had fallen asleep for 2 seconds, missing not only the sleep.
flash 6 inches from his nose but also the awareness of the abrupt moment of entry into sleep.
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